Global searching. Search for regex and move point to that position.
Nothing means reuse the last regular expression. Just s means use
s as the new regular expression. Direction of search can be
specified as either Backward or Forward (forwards in the buffer).
Arguments to modify the compiled regular expression can be supplied
as well.

Batch search-replace

Search and Replace all within the current region.
Note the region is the final argument since we might perform
the same search and replace over multiple regions however we are
unlikely to perform several search and replaces over the same region
since the first such may change the bounds of the region.